Method and apparatus for filtering



Feb. 1o, 1942. I g, `F, AJORDAN 2,272,175

METIOD AND APPARATUS FORHFILTERING F11-ed ot. 1, 1938 v ATTORNEYS Patented Feb. `10, 942

' Mirrnon AND APPARATUS Foa FILTERING Hubert F. Jordan, Nutley, NQJ., assigner, ,by

mesne'assi'gnments, to United States Rubber.'

Company, New York, N. Y., a corporation of New Jersey,

' Applicationetoberi, 1938, Serial No. 232,771

. 2 Claims.

l',Ihis inventionrelates to methods and apparatus for filtering, and more particularly for centrifugally filtering or separating comminuted material which is suspended or'dispersed in a fiuid medium.

Finely dividedfmaterial suspended in a liquidi has previously been centrifugally filtered by introducing the material vinto va, centrifugal filtering apparatus and expressing the filtrate therefrom through a filter medium which is'attached to a rotatable rigid frame The usual material employed .as a filtering medium in such constructions is wire fabric or woven fibrous fabric of sufficiently finemesh to retain the sus'-,v l

pended particles within the apparatus while allowing the filtrate to be separated by centrifugal force. lAfter using the apparatus for filtering a quantity of material, the filter medium becomes less efficient, 'that is, the interstices between the wires or fibres of the material used as the medium become clogged with solid particles. .as a result, itis necessaryto cleanout the filtering medium, which step` involves, especially in the case of fibrous fabric, removing the material from the framework of the apparatus and washing it to disengage the clogged particles -from the holes in which they are entrapped, and .finally replacing-the material. Alternatively, especially in the c-ase of wire mesh, fiuid rna'y be driven underpressure from Ajets through `certain of the interstices in the material to unclog it.- In practice, however, a great'number ofthe interstices in the filter medium become so tightly'clogged with solid material that fluid pressure alone fails to lclean it.` e f In filtering comminuted material itis at t-irnesv desired to separate and retain particles-of 4a. se#

lected minimum size and to permit particles ,y

lsmaller than that size to pass through the` filter in suspension with the filtrate.' With'previous centrifugal filters, this wasaccomplished by emL ploying a filter medium having a mesh size corresponding to the selected minimum size of ythe .particles to beA retained within the apparatus. When it was desired to let larger particles pass thro h the filter medium, it was necessary to replace the erigina1 medium with-materia having-a coarser msh.

According to. the present invention, a centrif.`

ugal filter is provided in which the filtering mespaced from,the first head and adjustable axial7 ly relative thereto,` ,A perforate elastic filtering I medium, for example, a perforate or foraminous rubber sheet, is secured to the heads and around the edges thereof so as to enclose the space vbe'- tween the heads, thereby forming a chamber from which the filtrate may beexpressed. When the adjustable head is moved axially'away vfrom the head which is secured to theshaft, the lter medium is stretchedand the perforations therein arel thereby enlagedf The degree of adjustment of the movable head may be predetermined to enlarge the perforations in the filter vmedium tothe desired extent.l I

The apparatus of jthe present invention may be conveniently and effectively cleaned or washed without removal of the filter .medium therefrom. When the perforations are enlargedl'by stretching the filter medium, the material clogging them' is Vimmediately loosened Aandymay be forced out by the application of fluid pressure. The elimination of the necessity for removal of the filter medium during the cleaning step obviously results in increased time and -labor efliiciency.. l

Inaddition, the present device may be so adjusted that when itis in one position particles having a given desired minimum size may be filtered; and in another position the filter medium mayy be stretched to enlarge the perforations so that the minimum size of the filtered particles is greater than those originally filtered. This result may be accomplished merely by adjustment dium may be completely cleaned .'insitu, without' I,

removal .from the apparatus. "Ihe apparatus y comprises, `generally,-a rotatable shaft, av headl -Q secured thereto kand rotatable with the shaft, and'1 Fig. 3 is a greatly enlarged plan view of suite able filtering, material in relaxed condition; and Fig. ,f1 lis a. plan view of the material shown in Fig. 3 vin stretched condition.

Referring'to the drawing, Figs. 1 and`2 illustrate anapplication of the principle. o'f the in- Ivention toa centrifugal filter having a hollow t shaft' i,fjournaledin a. base il,` andwhich may be driven by a belt 3 engaging a pulley 4 secured7 to the "shaft `The belt 3 may be driven by any e suitable driving means, and the upper portion L efuiesheft maybe extended and rotatably sup- J ported gbyxconvenient means .(not shown. An 'a second head also rotatable with the shaft buts `upperhead 5 comprisinga spider 6 supporting Aat the desired speed by thedriving belt 3. material to be filtered is introduced through thel a rim l is secured to the upper 'portion of the shaft by a set screw 8, to constitute an upper support for the filter medium. A cover disc 9 may be conveniently secured to the upper head in any desired manner. An adjustable head II, similar tothe upper head and comprising a spider I2 supporting a rim I3, is spaced from thed upper head 5 and secured for rotation with the shaft I. A collar I4 in the spider I2 has a keyway I5 which slidably engages an Aaxially projecting key I6 on the shaft I. The lower ends I1 of elongated pins I8 are secured to the arms of the spider I2 and extend upwardly to slid-` ably engage holes I9 which pass through the I8 terminate in stops 2|. I

Secured to the rim I3, a funnel shaped recep- `tacle 22 terminates downwardly in a double flanged collar 23 encircling the shaft I. The receptacle 22 is provided with an exit for filtered 3l i the filter medium 29 have become clogged, the filter cake may be removed by adjusting the fork ,25 to raise the collar 23 on the shaft I.

. When the collar 23 is raised, the keyway I5 in 5 the adjustable head II rises along the key I6 10 gated pins I8 slide in the holes I9 and the keyvway I5 of the collar I4 slides along the key I6. At the same time, since the filter medium 29 is exible, folds are produced therein so that pieces of the illter cake then drop into the receptacle 22 from whence they may be removed through the manhole 24. may be desirable to support the lter medium with a cylinder of inextensible material, such as wire gauze, to prevent excessive bulging of the elastic sheet 29. If desired, the apparatus may material which may conveniently take the form of a manhole 24. Adjustability for the head II together with the receptacle 22 is provided for by a fork 25 pivoted to a fixed upright 26. The fork 25 is provided with curved tines 21, each having an inwardly projecting pin 28, which extends radially with respect to the shaft I and terminates between the flanges of the collar 23; The tines 21 are so spaced so that when the fork is moved they may assume an -angular position with respect to the anges on the collar 23, so that the pins 29 are controlled to move the collar axially along the shaft I.

An elastic lter medium 29 is secured by any suitable means (not shown) to the heads 5 and II respectively, as by attaching it,to the external periphery of the rims 1 and I3 respectively. In the embodiment shown in Figs. 1 and 2, the filter medium 29 is in the form of a cylinder enclosing the space between the heads 5 and II respectively. The elastic filter medium 29, as shown in Figs. 3 and 4, may conveniently comprise a rubber sheet having perforations 3l therein. and it may be stretched by lowering the adjustable head II. The medium may be retained in its stretched condition by tightening a set screw 30 on the collar 23. Suitable material for 'the perforate elastic filter medium is described in U. S. patent to Linscott and Rice No. 2,032,941. In lieu ofthe perforations 3| the nlter medium may be provided with longitudinal. cuts or slits, and the perforations 3| may be of any desired size. shape, and arrangement.v

For introduction of materialto be filtered into the ltering apparatus, a pipe,32 may extend into the;upper opening of the hollow shaft I, and an inlet 33 may be provided in the form of a hole .in the upper portion of the shaft below the cover disc 9. In order to insure entrance of the mathe shaft I.

In operation, the apparatuses a unit`is revolved pipe 32 and enters the filter chamber, indicated by the numeral 35, through the inlet 33; Centrlfugal force drives the material to be ltered against the interior wall of the filter medium 29 and forces the ltrate through the perforations 3l therein, while retaining the ltered niaterial in the f'orm of a filter cake 36. When the be placed within a cylindrical catch wall (not shown) to control the travel of the filtrate after emerging from the filter medium.

After the filtering operation, the pores. 3|. in

25 the elastic sheet 29 are often clogged, vas above the original diameter.

described, with particles of the filtered material.

The pores or perforations 3l may conveniently` be cleaned and cleared of the clogging material by lowering the head II to stretch the sheet, as shown in Fig. 4. Reference to Fig. 4, as contrasted with Fig. 3, shows that a one-way stretch Iimparted to the sheet changes the circular voids of given diameter to an elliptical shape, in which both the major and minor axes are greater than The material may be retained in its stretched position by tightening the set screw 30 so as to hold down the head II. It may then be washed while still in situ on the apparatus by any suitable washing means, such as 40 by the introduction of a fluid under pressure therethrough. After the perforations have been cleaned, the head II may be returned to its former position and the sheet material 29 relaxed, whereupon the perforations may re-assume their original size and shape.

forations 3| as shown in Fig. 3. The operation may then be stopped and the filtered material removed, after which the filter medium is stretched by lowering the collar 23 and fixing 5r it Vin its lower position by the set screw 30,

The

filter cake has been built up to vform a deposit of square inch. When slitted material is` employed,

the desired thickness, or when the perforati .is

a the material then being represented by-Fig. 4.

The material which was removed from the manhole 24v may then`be reintroduced, and again ltered, in which case comminuted material hav'- ing a particle size greater. than that of the perforations 3| in Fig. 3, but smaller than that of the-perforations shown in Fig. 4, will pass through the medium. Itis obvious that when this operation is again repeated with the perforations still larger than those shown in Fig. 4, material having a still different minimum particle sizewill remain in the illter.

The rubber sheet material described in U. S. Patent No. 2,032,941 (referred to above) has been found suitable for filtering material of very4 ne particle \size; for example, the filter sheet therein described may have perforations ranging in average diameter anywhere from 0.0i to f 0.2 mm. and numbering from 1000 to 10,000 per During the 'altering operation it it is preferable that theslits `extend circumferentially, so that when stretched axially the linellike openings may be enlarged to the desired degree. I

Ther sheet rubber may also, if desired, be backed with a stretchable fabric to reduce bowing out of the filter medium 29,-which may oc- 1 I 3 1. A centrifugal lter comprising a rotatable shaft, a head secured to and rotatable with said cur due to the centrifugal action of the apparatus in operation. The perforationsv 3| may be produced in any desired manner, such as by punching or piercing the sheet material with needles.

The term rubber as herein referred to, broadly includes natural or artificial rubber or rubberlike material. The term "filtering comminuted material, is used herein to include broadly the filtration and separation, in the wet or dry state, of particles having different dimensions.

V While certain present preferred 4embodiments of the invention have'been shown and described, it will be understood that vit may otherwise be Having thus described my mventiommhat I claim andy desire to protect by Letters Patent is:

y. embodied lWithin the spirit thereof and within the scopeof the appended claims.

' ing the adjustable head relative to the first head to stretch the elastic sheet and td enlarge the perforations therein.

.2. A centrifugal lter comprising a rotatable shaft, a head secured to and rotatable with said shaft, a second head spaced fromsaid rst head1 and mounted on said shaft for rotation therewith and adjustable axially thereon, a` filter medium comprising a perforate elastic sheet material securedv to said heads and enclosing thespace between said heads, and means for securing the adjustable head in the desired axial position relative to the rst head Yto control the size of the perforations in the filter medium. 4

HUBERT F. JQRDAN. 

